Method for galvanizing steel member of support for solar photovoltaic or photothermal system

ABSTRACT

Disclosed is a method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, which relates to metal surface treatment. The method includes: subjecting the steel member to phosphorus-free degreasing and then pickling; dipping the steel member in a flux solution; drying the steel member; and subjecting the steel member to hot-dip galvanization, cooling and passivation to produce galvanized steel member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Chinese Patent Application No. 201910973663.4, filed on Oct. 14, 2019. The content of the aforementioned applications, including any intervening amendments thereto, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to metal surface treatment, and more particularly to a method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system.

BACKGROUND

Support structures for solar photovoltaic or photothermal systems are required to ensure the safe operation of the solar photovoltaic or photothermal systems, and have relatively low cost. Considering the practical needs of the existing photovoltaic or photothermal systems, angle iron and wood supports no longer meet the requirements of large-scale power generation for the characteristics, such as pressure resistance, corrosion resistance and maintenance-free, and aluminum alloy supports are not suitable for use in areas with high wind speed. Therefore, galvanized steel members show great advantages when used in a solar photovoltaic or photothermal support system. However, the existing galvanizing methods generally have the problems of unreasonable process, poor operating environment, high energy consumption and unstable product quality. Further, the galvanized steel members have poor corrosion resistance, and thus they are not suitable for use in some cold and saline-alkaline areas.

SUMMARY

An object of the invention is to provide a method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, which has simple process and good operation environment. The galvanization method provided herein can render the steel member of the support for the solar photovoltaic or photothermal system stable in performance and high in corrosion resistance.

Technical solutions of this application are described as follows.

This application provides a method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, comprising:

subjecting the steel member of the support for the solar photovoltaic or photothermal system to phosphorus-free degreasing and then pickling;

dipping the steel member in a flux solution;

drying the steel member; and

subjecting the steel member to hot-dip galvanization, cooling and passivation to produce galvanized steel member.

In some embodiments, a degreasing agent used in the phosphorus-free degreasing is an aqueous solution of an OP emulsifier, wherein the OP emulsifier in the degreasing agent is 2-3% by weight.

In some embodiments, the phosphorus-free degreasing is performed at 25-45° C. for 25-30 min.

In some embodiments, an acid used in the pickling is a 15-25% hydrochloric acid solution; and the pickling is performed at room temperature.

In some embodiments, the method further comprises:

after the pickling, rinsing the steel member with water.

In some embodiments, the flux solution is an aqueous solution of a mixture of zinc chloride and ammonium chloride; a total percent by weight of zinc chloride and ammonium chloride in the aqueous solution is 20-30%; and a weight ratio of ammonium chloride to zinc chloride is 0.8-1.6:1.

In some embodiments, a temperature of the flux solution is 55-65° C.

In some embodiments, a hot-dip galvanization temperature is 436-440° C.

In some embodiments, the cooling is performed with water; and the steel member is cooled to 45-47° C. through water cooling.

In some embodiments, a passivation solution used in the passivation is a mixed solution of aluminate and a water-soluble acrylic resin; and a weight ratio of the aluminate to the water-soluble acrylic resin in the mixed solution is 1:3.

The method provided herein for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, including: subjecting the steel member of the support for the solar photovoltaic or photothermal system to phosphorus-free degreasing and then pickling; dipping the steel member in a flux solution; drying the steel member; and subjecting the steel member to hot-dip galvanization, cooling and passivation to produce galvanized steel member. The method provided herein has simple process, good operation environment, high efficiency and low cost. The steel member galvanized through the method provided herein is stable in performance and high in corrosion resistance.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention provides a method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, including:

subjecting the steel member of the support for the solar photovoltaic or photothermal system to phosphorus-free degreasing and then pickling;

dipping the steel member in a flux solution;

drying the steel member; and

subjecting the steel member to hot-dip galvanization, cooling and passivation to produce galvanized steel member.

The phosphorus-free degreasing is performed by immersing the steel member in a degreasing agent, where the degreasing agent is an aqueous solution of 2-3%, preferably 2.5%, by weight of an OP emulsifier. A main component of the OP emulsifier is alkylphenol ethoxylates. A temperature of the phosphorus-free degreasing is 25-45° C., preferably 30-35° C.; and a time of the phosphorus-free degreasing is 25-30 min, preferably 26-28 min. The temperature of the phosphorus-free degreasing actually refers to the temperature of the degreasing agent, and the time of the phosphorus-free degreasing is the immersion time of the steel member in the degreasing agent. The oil pollutants on the surface of the steel member can be removed through the phosphorus-free degreasing.

After the phosphorus-free degreasing is completed, the steel member is subjected to pickling. An acid used in the pickling is a 15-25%, preferably 18-22%, hydrochloric acid. The pickling is preferably performed at room temperature. The oxide on the surface of the steel member is removed though the pickling. After the pickling, the steel member is preferably subjected to water rinsing to remove residual acid on the surface. The water rinsing is preferably performed 2 times. The waste acid (waste hydrochloric acid) can be recovered by acid mist absorption, thereby achieving the reuse of the hydrochloric acid. Specifically, the waste acid is evaporated with flame or steam, and then subjected to condensation.

The steel member of the support for the solar photovoltaic or photothermal system is dipped in a flux solution after the pickling is completed. The flux solution is an aqueous solution of a mixture of zinc chloride and ammonium chloride, where a total percent by weight of zinc chloride and ammonium chloride in the aqueous solution is 20-30%, preferably 25-26%; a weight ratio of the ammonium chloride to the zinc chloride is 0.8-1.6:1, preferably 1.2-1.5:1. A temperature of the flux solution is 55-65° C., preferably 60° C.; a dipping time is 40-90 seconds, preferably 50-70 seconds. The dipping in the flux solution enables the iron of the steel member to better bond the zinc layer in the following hot dip galvanization. Fe²⁺ will present in the flux solution after use, which would affect the performance of the flux solution. In order to realize the reuse of the flux solution, an oxidizing agent can be used to oxidize the Fe²⁺ to Fe³⁺, which can be easily removed in the form of Fe(OH)₃. The reuse of the flux solution will facilitate the energy saving and emission reduction of the galvanizing process.

The steel member is then dried at 50-70° C. for 50-70 s.

The dried steel member is subsequently subjected to hot dip galvanization, that is, the steel member is dipped in a molten zinc bath. A hot dip galvanization temperature is 436-440° C., preferably 438° C. The hot dip galvanization temperature actually refers to the temperature of the molten zinc bath. The hot dip galvanization is performed for 5-10 min, preferably 6-8 min.

After the hot dip galvanization is completed, the steel member is sequentially subjected to cooling and passivation. The cooling is preferably performed with water, and the steel member is cooled to 45-47° C. The water cooling can guarantee the gloss of the final products. A passivation solution for the passivation is preferably a mixed solution of aluminate and a water-soluble acrylic resin, where a weight ratio of the aluminate to the water-soluble acrylic resin in the mixed solution is preferably 1:3. The passivation is preferably performed at 50-60° C. for 40-90 min. Through the passivation process, a passivation film is formed on the surface of the galvanized steel member of the support of the photovoltaic or photothermal system.

The method of the invention has simple process, good operation environment, high efficiency and low cost. The steel member galvanized through the method provided herein is stable in performance and high in corrosion resistance.

The invention will be described in detail below with reference to the embodiments. It should be understood that these embodiments are not intended to limit the scope of the invention.

Example 1

Provided herein was a method for galvanizing a steel member of support for a solar photovoltaic system, which was specifically described as follows.

(1) The steel member of the support for the solar photovoltaic system was subjected to phosphorus-free degreasing, where the phosphorus-free degreasing was performed in an aqueous solution of an OP emulsifier at 25° C. for 25 min, and the OP emulsifier in the aqueous solution was 2% by weight .

(2) The steel member was subjected to pickling to remove the metal oxide on the surface, where an acid used in the pickling was 15% hydrochloric acid, and the pickling was performed at room temperature. After the pickling was completed, the steel member was rinsed with water.

(3) The steel member was dipped in a flux solution and dried, where the flux solution was an aqueous solution of a mixture of zinc chloride and ammonium chloride; a total percent by weight of the zinc chloride and ammonium chloride in the aqueous solution was 20%; a weight ratio of ammonium chloride to zinc chloride was 1.2:1; and a temperature of the flux solution was 55° C.

(4) The steel member was subjected to hot dip galvanization at 440° C.

(5) The galvanized steel member of the solar photovoltaic support system was cooled to 45° C. with water.

(6) The galvanized steel member was passivated in a passivation solution, where the passivation solution was a mixed solution of aluminate and water-soluble acrylic resin in a weight ratio of 1:3.

(7) The galvanized steel member was checked and stored.

The galvanized steel member of the support for the solar photovoltaic system was tested for the corrosion resistance according to GB6458-86 “Salt Spray Tests”. After treated by acid salt spray for 480 h, the galvanized steel member merely suffered a loss of 23 μm in the thickness.

Example 2

Provided herein was a method for galvanizing a steel member of a support for a solar photothermal system, which was specifically described as follows.

(1) The steel member of the support for the solar photovoltaic system was subjected to phosphorus-free degreasing, where the phosphorus-free degreasing was performed in an aqueous solution of an OP emulsifier at 45° C. for 30 min, where the OP emulsifier in the aqueous solution was 3% by weight.

(2) The steel member was subjected to pickling to remove the metal oxide on the surface, where an acid used in the pickling was 25% hydrochloric acid, and the pickling was performed at room temperature. After the pickling was completed, the steel member was rinsed with water.

(3) The steel member was dipped in a flux solution and dried, where the flux solution was an aqueous solution of a mixture of zinc chloride and ammonium chloride; a total percent by weight of the zinc chloride and ammonium chloride in the aqueous solution was 30%; a weight ratio of ammonium chloride to zinc chloride was 1.6:1; and a temperature of the flux solution was 60° C.

(4) The steel member was subjected to hot dip galvanization at 436° C.

(5) The galvanized steel member was cooled to 47° C. with water.

(6) The galvanized steel member was passivated in a passivation solution, where the passivation solution was a mixed solution of aluminate and water-soluble acrylic resin in a weight ratio of 1:3.

(7) The galvanized steel member was checked and stored.

The galvanized steel member of the support for the solar photothermal system was tested for the corrosion resistance according to GB6458-86 “Salt Spray Tests”. After treated by acid salt spray for 480 h, the galvanized steel member merely suffered a loss of 21 μm in the thickness.

The above embodiments show that after galvanized through the method of the invention, the steel member of the solar photovoltaic or photothermal support system exhibits stable performance and high corrosion resistance. Meanwhile, the method of the invention has simple process, good operation environment, high efficiency and low cost.

Described above are merely preferred embodiments of the invention, and it should be noted that various modifications and replacements made by those skilled in the art without departing from the spirit of the invention should fall within the scope of the invention. 

What is claimed is:
 1. A method for galvanizing a steel member of a support for a solar photovoltaic or photothermal system, comprising: subjecting the steel member of the solar photovoltaic or photothermal support system to phosphorus-free degreasing and then pickling; dipping the steel member in a flux solution; drying the steel member; and subjecting the steel member to hot-dip galvanization, cooling and passivation to produce galvanized steel member.
 2. The method of claim 1, wherein a degreasing agent used in the phosphorus-free degreasing is an aqueous solution of an OP emulsifier; and the OP emulsifier in the degreasing agent is 2-3% by weight.
 3. The method of claim 1, wherein the phosphorus-free degreasing is performed at 25-45° C. for 25-30 min.
 4. The method of claim 2, wherein the phosphorus-free degreasing is performed at 25-45° C. for 25-30 min.
 5. The method of claim 1, wherein an acid used in the pickling is a 15-25% hydrochloric acid solution; and the pickling is performed at room temperature.
 6. The method of claim 1, further comprising: after the pickling, rinsing the steel member with water.
 7. The method of claim 5, further comprising: after the pickling, rinsing the steel member with water.
 8. The method of claim 1, wherein the flux solution is an aqueous solution of a mixture of zinc chloride and ammonium chloride; a total percent by weight of zinc chloride and ammonium chloride in the aqueous solution is 20-30%; and a weight ratio of ammonium chloride to zinc chloride is 0.8-1.6:1.
 9. The method of claim 1, wherein a temperature of the flux solution is 55-65° C.
 10. The method of claim 8, wherein a temperature of the flux solution is 55-65° C.
 11. The method of claim 1, wherein a hot-dip galvanization temperature is 436-440° C.
 12. The method of claim 1, wherein the cooling is performed with water; and the steel member is cooled to 45-47° C. through water cooling.
 13. The method of claim 1, wherein a passivation solution used in the passivation is a mixed solution of aluminate and a water-soluble acrylic resin; and a weight ratio of the aluminate to the water-soluble acrylic resin in the mixed solution is 1:3. 